1. Field of the Invention
The present invention relates to a conductive polymer film and a method of producing the film, and an electronic device using the conductive polymer film and a method of producing the device.
2. Description of the Related Art
Conductive polymers each have characteristics such as excellent flexibility and an excellent lightweight characteristic while having metallic electronic conductivity or semiconductivity.
The conductive polymers have been conventionally used in the fields of, for example, antistatic materials, cathode materials for solid electrolytic capacitors, electromagnetic wave-shielding materials, transparent electrode materials, and antirust materials by taking advantage of their characteristics. In addition, research has been conducted on the application of the polymers to conductive film materials for use in electronic devices such as solid electrolytic capacitors, organic electroluminescent devices, actuators, transistors, solar cells, touch panels, and various sensors.
It has been known that, in the case of, for example, a solid electrolytic capacitor, an increase in conductivity of a conductive polymer film to be used as its cathode can reduce an equivalent series resistance (hereinafter referred to as “ESR”) as an important value for evaluating the solid electrolytic capacitor for its characteristic. Research and development toward an increase in conductivity of the conductive polymer film have been advanced because the conductivity of the conductive polymer film serves as an important factor for the performance of such electronic device.
In recent years, investigation has been conducted on the introduction of various additives to a conductive polymer as an approach to increasing the conductivity of the conductive polymer film. To be specific, various proposals have been made on the use of, firstly, an “organic solvent”, secondly, a “basic compound”, and thirdly, an “acid substance” as such additives, and the solvent, the compound, and the substance are introduced below.
With regard to the “organic solvent” as the first additive, for example, the addition of an organic solvent such as N-methylpyrrolidone or ethylene glycol to a conductive polymer formed of a polythiophene and a polyanion has been proposed (Japanese Patent No. 2916098). With regard to the “basic compound” as the second additive, for example, the addition of a basic conductivity improver to a conductive polymer formed of a conductive polymer and a polyanion has been proposed (Japanese Patent Application Laid-Open No. 2007-95506). In addition, it has been proposed that a basic conductivity improver is added to a monomer for a conductive polymer and the mixture is subjected to oxidative polymerization (Japanese Patent Application Laid-Open No. 2008-171761 and Advanced Functional Materials 2004, 14, P615). With regard to the “acid substance” as the third additive, it has been proposed that an acid additive such as p-toluenesulfonic acid or an aromatic dicarboxylic acid is added to a monomer for a conductive polymer and the mixture is subjected to oxidative polymerization (Japanese Patent Application Laid-Open No. 2009-107552 and Japanese Patent Application Laid-Open. No. 2008-34440).